ON THEORIES OF THE EARTH. 397 



But if, although what is impossible cannot be true, it 

 may still be believed, as experience has here shown, it 

 is not always easy to believe against the evidence of the 

 vulgar senses. The strata are not universal, nor every 

 where in the same order, nor do they appear at suc- 

 cessively lower levels. The antient rocks are not all 

 purely chemical, nor the recent ones mechanical ; while, 

 even here, the theory contradicts itself, with its crys- 

 tallized conglomerates. 



Nor does any chemistry explain why one rock was 

 replaced by another, why the same compound assumed 

 so many forms and positions, why one only was preci- 

 pitated at once, why silica gave way to clay, why there 

 are repetitions of the same rocks, why serpentine and 

 others are so partial, and why, and whence, the ocean 

 acquired its new materials, after having become clear 

 for the habitation of animals. The " limestone forma- 

 tion suite" contradicts what it is adduced to prove; to 

 explain the forms of strata by crystallization, is to use 

 a term without meaning; and to call a vein contem- 

 poraneous with its including rock, is to be ignorant of 

 the use of words. The theory of coal does riot deserve 

 a remark: and it belongs to this system, peculiarly, to 

 have adopted the most impossible one respecting mi- 

 neral veins. On volcanoes, I need only notice the 

 overbearing confidence of the assertions; and, while 

 grievously ignorant of organic fossils, there is not a fact 

 respecting them which does not overturn the whole 

 system. But more than enough: odious as is the task, 

 such criticism is a needful branch of geological in- 

 struction: and what I have here said, I may suppress 

 as to future similar speculations. 



De Luc attempts to remedy some defects in this sys- 

 tem, by borrowing from Saussure ; whence his claims 

 to originality are but trifling, as they are not enviable. 



